Sahara dust outbreak across the Western Mediterranean.
09 August 2021
28 July 2005
by Jochen Kerkmann and HansPeter Roesli (EUMETSAT)
Sahara dust outbreaks towards the Mediterranean Sea or the Atlantic Ocean are very common throughout the year, with a peak frequency in spring (March, April, May). The Meteosat-8 images below show two RGB composites that help to detect dust outbreaks: the left image shows the so-called dust RGB, which is designed to monitor the evolution of dust storms mainly over deserts during both day and night (dust appears pink or magenta).
This RGB composite does allow however the further (24 hour) tracking of dust clouds as they spread over the sea (see animation). In practice, during the daytime the use of visible channels (in particular the HRV channel) is preferable for the tracking of dust over the sea. This can be seen in the right image, which gives a detailed view of the dust cloud as it reaches Sardinia and Sicily.
In this RGB composite, the dust is best visible in the morning hours due to the strong forward scattering of the solar radiation on the dust particles, which are of roughly the same size as the wavelength of the incident solar radiation. During local noon, when Sun and satellite are looking with nearly the same angle at the dust cloud, the dust becomes almost invisible.
RGB composite (time average) (27 July 14:00 UTC–28 July 24:00 UTC)
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